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About Glazes: Article or Project

What are Glazes?

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Simply put, glazes are glass. Broken down to its original state, it is silica/glass powder, suspended in a liquid with chemicals added to create a multitude of special effects and colors. When subjected to high heat, these all melt down and blend to create a flowing sheet or coating to whatever they are placed on. When cooled, they are a sheet of glass covering the bisque clay item.


The higher the sheen and more translucent the finish, the more glass content. The more opaque or less shine, the less glass in the glaze. Glazes range from Matte to High Gloss and Translucent to Opaque. Translucent glazes are sheer and you can see through them, the most translucent being Clear Glaze. Semi-translucent glazes are somewhat sheer, but color settles in crevices creating a denser color. Semi -Opaque, still have a small amount of translucency, but not a lot. Opaque glazes are the most dense and you cannot see through the fired finish.

All ceramic glazes need to be subjected to the correct temperature heat in order to maximize their color and glass-like appearance. Be sure to follow manufacturer instructions on the labels.

Gloss Glazes are higher in glass content and have a shiny, glossy finish and are available in a wide variety of colors. These glazes flow more during the firing process and include the following classifications Transparent Gloss glazes are very transparent; Semi-Gloss Glazes are somewhat transparent; Semi-Opaque Gloss Glazes are less transparent, but not quite opaque and finally Opaque Gloss Glazes are non-transparent, you cannot see through them.

Matte Glazes are very beautiful and have a softer appearance. Because they have less glass content, they flow less during the firing process. These have the same classifications as the Gloss Glazes and come in a wide variety of color selections. One of the disadvantages of matte glazes is that they can be hard to clean and can have a rougher finish.

Another classification of glazes are special effects. These include break-up glazes, spill, pattern, cascading and draping glazes. They are most often designed to go over or between other glazes to produce drippy, lacy, or blended effects. Crystal glazes are made up of basic colors of gloss or matte glazes that have small glass crystals added. During firing, the crystals drip and flow on vertical pieces and spread out on horizontal surfaces. In using any of these specialty glazes, control is very important. They require practice, skill and judgment of application. Errors in application can make the difference between mediocre or exceptional results.

Additional Specialty glazes include wood-tone, art glazes, snow, bead, crackle glazes and also textural glazes. Wood-tone glazes are a matte glazes with beads of color pigment in them that when applied, the beads burst and leave streaks looking like wood grain. Crackle glazes are designed to crack after firing creating a web-like pattern of thin broken lines throughout the surface. (Note: crackle glazes look like, but should not be confused with crazing which is a flaw in the finish) Art glazes are usually two toned glazes that flow and settle unevenly creating unique individualism. Snow puffs up to give a frothy appearance. Bead breaks up and creates a rounded, bead-like texture. Texture glazes are really an underglaze product with specks of glass in them creating a contrast in shine and surface texture.

Relatively new in the field of ceramics products are the bumpy, raised detail glazes. These apply very thick and are great for raised design, embossing and detailing. These usually have a high sheen, but are formulated to not flow. Most can go on top of matte glazes or under gloss glazes.

 

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